Communication systems are known to transport large amounts of data between a plurality of end user devices, which, for example, include telephones, facsimile machines, computers, television sets, cellular telephones, personal digital assistants, et cetera. As is also known, such communication systems may be local area networks (LAN) and/or wide area networks (WAN) that are stand-alone communication systems or interconnected to other local area networks and/or wide area networks as part of the public switched telephone network, public switched data network, integrated service digital network, the Internet, et cetera. As is further known, communication systems include a plurality of system equipment to facilitate the transporting of data. Such system equipment includes, but is not limited to, routers, switches, bridges, gateways, protocol converters, frame relays, private branch exchanges, et cetera.
The transportation of data within communication systems is governed by one or more standards that ensure the integrity of data conveyances and fairness of access for data conveyances. For example, there are a variety of Ethernet standards that govern serial transmissions within a communication system at data rates of 10 megabits per second, 100 megabits per second, 1 gigabit-per-second and beyond. In accordance with such standards, many system components and end user devices of a communication system transport data via serial transmission paths. Internally, however, the system components and end user devices process data in a parallel manner. As such, each system component and end user device includes at least one high-speed transceiver, which includes a high-speed serial-to-parallel receiver and a high-speed parallel-to-serial transmitter.
As the demand for data throughput increases, so do the demands on the high-speed transceiver. The increased throughput demands are pushing some current integrated circuit manufacturing processes to their operating limits, where integrated circuit processing limits (e.g., device parasitics, trace sizes, propagation delays, device sizes, et cetera) and IC fabrication limits (e.g., IC layout, frequency response of the packaging, frequency response of bonding wires, et cetera) limit the speed at which a high-speed transceiver may operate, jitter performance, and/or noise performance. Such limitations are forcing transceiver designers to seek alternative implementations. For instance, some designers are electing to use multiple serial paths coupled in parallel to transmit data at higher rates. For example, to obtain a 10 gigabit-per-second path, four 3.125 gigabit-per-second transceivers are bonded together to function as a 10 gigabit-per-second transceiver. The bonding requires that each 3.125 gigabit-per-second path operate in a known and controlled relationship with respect to the other paths such that transceived data can be accurately transmitted and subsequently reconstructed. As such, additional circuitry is needed to achieve the bonding and additional buses are needed to transport the bonded data. As is known, each bus requires a separate driver to mitigate transmission line effects of the bus, thus, each additional bus requires an additional driver, which increases power consumption.
Another alternate high-speed transceiver implementation is to use multilevel encoding over a single bus. As is known, multilevel encoding uses various voltage levels to indicate the value of data currently being transmitted. For example, four different voltage levels may be used to represent two bits of data. For accuracy of transmission, the difference between each voltage level should be significant enough to readily distinguish them at the receiving end. This becomes more difficult as the supply voltages of the integrated circuit decrease with improvements in integrated circuit fabrication processes. For instance, 0.10 micron CMOS technology allows integrated circuits to be powered from a supply voltage of approximately 1 volt.
A further alternative for transceivers is to use an integrated circuit technology that inherently provides for greater speeds. For instance, switching from a CMOS process to a silicon germanium or gallium arsenide process would allow integrated circuit transceivers to operate at greater speeds, but at substantially increased manufacturing costs. Currently, for most commercial-grade applications, including communication systems, such alternate integrated circuit fabrication processes are too cost prohibitive for wide spread use.
Therefore, a need exists for a high-speed transceiver that operates at rates, which push the operating limits of the IC fabrication process, meets desired jitter performance requirements and noise requirements, does so without requiring bonding of multiple transceivers to achieve the desired rate, and does so for a given IC fabrication process.